Liquid crystal display device and method of manufacturing the same

ABSTRACT

A liquid crystal display (LCD) device and method of manufacturing the same are provided. The LCD comprises, a first substrate, a second substrate facing the first substrate, a liquid crystal layer interposed between the first substrate and the second substrate and includes liquid crystal molecules, an alignment film disposed between the liquid crystal layer and the first substrate, a pixel electrode disposed between the alignment film and the first substrate, a photo-curable layer between the liquid crystal layer and the alignment films, a common electrode disposed between the liquid crystal layer and the second substrate, and a vertical alignment inducing layer between the common electrode and the liquid crystal layer. The vertical alignment inducing layer includes a self-aligned vertical alignment inducer, and the vertical alignment inducer includes a hydrophilic group, and an affinity liquid crystal group having high affinity with the liquid crystal molecules.

This application is a divisional of U.S. patent application Ser. No.15/002,084, filed on Jan. 20, 2016, which claims priority from KoreanPatent Application No. 10-2015-0106567 filed on Jul. 28, 2015, and allthe benefits accruing therefrom under 35 U.S.C. § 119, the content ofwhich in its entirety is herein incorporated by reference.

BACKGROUND 1. Field of the Invention

The invention relates to a liquid crystal display device and a method ofmanufacturing the liquid crystal display device.

2. Description of the Related Art

Liquid crystal display devices are widely used in flat panel displaydevices, and include two substrates having field generating electrodessuch as a pixel electrode and a common electrode, and a liquid crystallayer interposed between the substrates.

The liquid crystal display device applies a voltage to the fieldgenerating electrode to generate an electric field in the liquid crystallayer, determines the alignment direction of the liquid crystals withinthe liquid crystal layer through the electric field, and displays animage by controlling the polarization of incident light.

When the liquid crystal display device is used as a display device for atelevision receiver, the size of the screen is increased. In this way,as the size of the liquid crystal display device increases, visualdifferences may also be increased depending on whether a viewer sees acentral portion of the screen or whether a viewer sees both left andright ends of the screen.

To compensate for these visual differences, the liquid crystal displaydevice may be formed into a curved shape by bending into a concave orconvex shape. The curved liquid crystal display device may be a portraittype which has a vertical length longer than a horizontal as observedfrom the perspective of a viewer, and is bent in a vertical direction.The curved liquid crystal display may also be a landscape type which hasa vertical length shorter than a horizontal length and is bent in ahorizontal direction.

SUMMARY

In a curved liquid crystal display device or a flexible liquid crystaldisplay device, as a display panel is bent, misalignment may occurbetween an upper substrate and a lower substrate. As a result, avertical line dark portion is visible within a pixel region. Further,the vertical line dark portion of the pixel region may be recognized asdirt by when observed by a viewer, or may be a reddish phenomenon inwhich colors are recognized as being reddish.

An aspect of the present invention provides a liquid crystal displaydevice capable of improving a display quality even in a curved orflexible liquid crystal display device.

Another aspect of the present invention provides a method ofmanufacturing the liquid crystal display device capable of improving thedisplay quality.

In various embodiments, the liquid crystal display (LCD) deviceincludes, a first substrate, a second substrate facing the firstsubstrate, a liquid crystal layer interposed between the first substrateand the second substrate and including liquid crystal molecules, analignment film disposed between the liquid crystal layer and the firstsubstrate, a pixel electrode disposed between the alignment film and thefirst substrate, a photo-curable layer between the liquid crystal layerand the alignment films, a common electrode disposed between the liquidcrystal layer and the second substrate, and a vertical alignmentinducing layer between the common electrode and the liquid crystallayer, wherein the vertical alignment inducing layer includes aself-aligned vertical alignment inducer, and the vertical alignmentinducer includes a hydrophilic group, and an affinity liquid crystalgroup having a high affinity with the liquid crystal molecules.

In an exemplary embodiment, the vertical alignment inducing layer may bedisposed on a surface of the common electrode.

In an exemplary embodiment, the hydrophilic group of the verticalalignment inducer may be aligned in a direction of the common electrode,the affinity liquid crystal group of the vertical alignment inducer maybe aligned in the direction of the liquid crystal layer, and thevertical alignment inducer may be self-aligned vertically with respectto the surface of the common electrode.

In an exemplary embodiment, the hydrophilic group may include one ormore of a hydroxyl group, an amino group and a thiol group.

In an exemplary embodiment, the alignment film may comprise includepolyimide having a main chain and one or more side chain, the polyimidemay include an a repeating unit of a main chain including an imidegroup, and at least a portion of the side chain may include a side chainsubstituted by a vertical alignment group and a side chain substitutedby a polymerization initiator.

In an exemplary embodiment, the photo-curable layer may be a reactionproduct of a photo-curable agent and the polymerization initiator.

In an exemplary embodiment, the photo-curable agent may include areactive mesogen.

In an exemplary embodiment, the side chain substituted by the verticalalignment group may have a pre-tilt.

In an exemplary embodiment, the liquid crystal molecules may havenegative dielectric anisotropy, the liquid crystal molecules includefirst liquid crystal molecules adjacent to the photo-curable layer, andsecond liquid crystal molecules adjacent to the vertical alignmentinducing layer, the first liquid crystal molecules may have a firstpre-tilt angle with respect to the first substrate in an initial statein which no electric field is formed, and the second liquid crystalmolecules may have a second pre-tilt angle smaller than the firstpre-tilt angle with respect to the second substrate.

In an exemplary embodiment, the second pre-tilt angle may be from 0° toabout 2° or less.

In an exemplary embodiment, the pixel electrode may be a patternelectrode having a slit pattern, and the pixel electrode may include aplurality of domains in which alignment directions of the liquid crystalmolecules are different from each other.

In an exemplary embodiment, one or more of the first substrate and thesecond substrate may be bent.

According to other embodiments, a method of manufacturing a LCD deviceincludes, preparing a first substrate having a pixel electrode formed onan upper surface of the first substrate, forming an alignment film onthe pixel electrode, preparing a second substrate having an commonelectrode formed on an upper surface of the second substrate anddisposing the second substrate such that the common electrode faces thealignment film, interposing a liquid crystal layer including a verticalalignment inducer between the alignment film and the common electrode,forming a vertical alignment inducing layer from the vertical alignmentinducer, forming an electric field between the pixel electrode and thecommon electrode, and irradiating light in the presence of the electricfield to form a photo-curable layer on the surface of the alignmentfilm.

In an exemplary embodiment, the liquid crystal layer may include aphoto-curable agent.

In an exemplary embodiment, the photo-curable layer may be formed bypolymerization of the photo-curing agent present in the liquid crystallayer.

In an exemplary embodiment, the alignment film may comprise aphoto-curable agent.

In an exemplary embodiment, the photo-curable layer formed may be formedby polymerization of the photo-curing agent present in the alignmentfilm.

In an exemplary embodiment, the vertical alignment inducer may be alinear molecule having a hydrophilic group capable of hydrogen bondingat one end, and an affinity crystal group having a high affinity withthe liquid crystal molecules at the other end, where the end having thehydrophilic group may be aligned in the direction of the commonelectrode, and the end having the affinity crystal group may be alignedin the direction of the liquid crystal layer to form a verticalalignment inducing layer on the surface of the common electrode.

In an exemplary embodiment, may further comprise irradiating light inthe absence of the electric field after the forming of the photo-curablelayer.

In an exemplary embodiment, the liquid crystal molecules adjacent to thephoto-curable layer have a first pre-tilt angle, and the liquid crystalmolecules adjacent to the vertical alignment inducing layer have asecond pre-tilt angle smaller than the first pre-tilt angle.

The liquid crystal display device of the present invention is capable ofsubstantially vertically aligning the liquid crystal molecules adjacentto the upper substrate, and aligning the liquid crystal moleculesadjacent to the lower substrate in a pre-tilt manner. Accordingly, it ispossible to improve light transmittance and to minimize the texture dueto the misalignment.

Moreover, it is possible to set the different pre-tilts of the liquidcrystal molecules adjacent to the upper substrate and the liquid crystalmolecules adjacent to the lower substrate without using differentalignment films on the upper substrate and the lower substrate. Theprocess thus can be simplified to reduce costs.

Also, it is possible to provide a liquid crystal display device withimproved reliability, by alleviating the dirt or the reddish phenomenongenerated in the display panel.

Effects according to the aspects of the present invention are notlimited by the contents illustrated above, and further various effectsare also included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantage and features of this disclosure willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings, in which:

FIG. 1 is a perspective view of an exemplary embodiment of a curvedliquid crystal display device according to the present invention;

FIG. 2 is an exploded perspective view of the liquid crystal displaydevice of FIG. 1;

FIG. 3 is an equivalent circuit diagram of a pixel (PX) of the exemplaryliquid crystal display in FIG. 2;

FIG. 4 is an enlarged plan view of a pixel of the exemplary liquidcrystal display in FIG. 2;

FIG. 5 is a cross-sectional view taken along line V-V′ of the exemplaryliquid crystal display in FIG. 4;

FIG. 6 is a cross-sectional view taken along line VI-VI′ of theexemplary liquid crystal display in FIG. 4;

FIG. 7 is a flowchart illustrating an exemplary process formanufacturing the liquid crystal display device according to the presentinvention;

FIGS. 8 to 14 are cross-sectional views illustrating the separatemanufacturing process steps of FIG. 7 in a stepwise manner, where 10(B)is an enlarged view of the circled portion of FIG. 10(A);

FIG. 15 is a flowchart illustrating another exemplary process ofmanufacturing the liquid crystal display device according to the presentinvention; and

FIGS. 16 to 22 are cross-sectional views illustrating the separatemanufacturing processes of FIG. 15 in a stepwise manner, where FIG.18(B) is an enlarged view of the circled portion of FIG. 18(A).

DETAILED DESCRIPTION

Features of the inventive concept and methods of accomplishing the samemay be understood more readily by reference to the following detaileddescription of preferred embodiments and the accompanying drawings.

The inventive concept may, however, be embodied in many different formsand should not be construed as being limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete and will fully convey theconcept of the inventive concept to those skilled in the art, and theinventive concept will only be defined by the appended claims.

In the drawings, the thickness of layers and regions are exaggerated forclarity. It will be understood that when an element or layer is referredto as being “on,” “connected to” or “coupled to” another element orlayer, the element or layer can be directly on, connected or coupled toanother element or layer, or intervening elements or layers may bepresent therebetween. In contrast, when an element is referred to asbeing “directly on,” “directly connected to” or “directly coupled to”another element or layer, there are no intervening elements or layerspresent. As used herein, “connected” refers to elements beingphysically, electrically and/or fluidly connected to each other.

Like numbers refer to like elements throughout. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

It will be understood that, although the terms “first,” “second,”“third,” etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, a “first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings of theinvention.

Spatially relative terms, such as “below,” “lower,” “bottom,” “under,”“above,” “top,” “upper” and the like, may be used herein for ease ofdescription to describe the relationship of one element or feature toanother element(s) or feature(s) as illustrated in the figures. It willbe understood that the spatially relative terms are intended toencompass different orientations of the device in use or operation, inaddition to the orientation depicted in the figures. For example, if thedevice in the figures is turned over, elements described as “below” or“beneath” relative to other elements or features would then be oriented“above” relative to the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (rotated 90 degrees or at otherorientations) and the spatially relative descriptors used hereininterpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used in thisspecification, specify the presence of stated features, integers,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10% or 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, embodiments of the present invention will be described withreference to the attached drawings.

FIG. 1 is a perspective view of an exemplary embodiment of a liquidcrystal display device. FIG. 2 is a schematic exploded perspective viewof the liquid crystal display device of FIG. 1.

Referring to FIGS. 1 and 2, a liquid crystal display device 10 includesa first substrate BS1, a second substrate BS2 which faces the firstsubstrate BS1 and is spaced apart from the first substrate BS1, and aliquid crystal layer 300 interposed between the first substrate BS1 andthe second substrate BS2. The first and second substrates BS1, BS2 are atransparent or an opaque insulating substrate, and may be, for example,a silicon substrate, a glass substrate, a plastic substrate, or thelike.

Each of the first substrate BS1 and the second substrate BS2 includes adisplay area DA and a non-display area NA. The display area DA is anarea in which an image is visually recognized, and the non-display areaNA is an area in which the image is not visually recognized. The areadefined by the display area DA is surrounded by the area defining thenon-display area NA.

The display area DA includes a plurality of gate lines GL which extendsubstantially parallel to one another along a first direction (e.g., arow direction), a plurality of data lines DL which extend substantiallyparallel to one another along a second direction (e.g., a columndirection) perpendicular to and intersecting with the first direction ofthe gate lines, and a plurality of pixels PX formed in a region in whichthe gate lines GL and data lines DL intersect with one another. Theplurality of pixels PX may be arranged in the row direction and thecolumn direction and may have a substantially matrix shape.

Each pixel PX may uniquely display one primary color so as to achievethe color display. Examples of the primary colors may include, red,green and blue, but is not limited thereto.

The non-display area NA may be a light-shielding area. A driving unit(not illustrated) which provides gate drive signals, data drive signalsand the like to the pixels PX of the display area DA may be disposed inthe non-display area NA of the first substrate BS1. The gate lines GLand the data lines DL may extend from the display area DA to thenon-display area NA and may be electrically connected the driving unit(not illustrated).

An alignment film (not illustrated) may be disposed on an upper surfaceof the first substrate BS1. A liquid crystal layer 300 may be interposedbetween the alignment film and the second substrate BS2. The liquidcrystal layer 300 may include liquid crystal molecules having a negativedielectric anisotropy, and may also include liquid crystal moleculeshaving a positive dielectric anisotropy, without being limited thereto.

As used herein, the row direction (the horizontal direction) of theliquid crystal display device 10 is referred to as a first direction X,and the column direction (i.e. the vertical direction) will be referredto as a second direction Y. As illustrated in FIGS. 1 and 2, the liquidcrystal display device 10 may be a curved liquid crystal display devicewhich is bent along a plane defined by the first direction X. Theexemplary embodiment of the curved liquid crystal display device isrepresented as a flat panel type liquid crystal display device in thefollowing cross-sectional views for convenience and ease of explanation.

FIG. 3 is an equivalent circuit diagram of a pixel of FIG. 2.

Referring to FIG. 3, an arbitrary pixel PX is connected to acorresponding gate line GLi, a data line DLj and a reference voltageline (not illustrated). Here, i and j are integers greater than 0. Thepixel PX may be provided with a data signal and a reference voltage Vrdis then provided from the data line DLj and the reference voltage linein response to the gate signal provided through the gate line GLi. Thereference voltage Vrd, for example, may be a constant voltage such as acommon voltage Vcom, or may be a voltage having the same polarity as thedata voltage with respect to the common voltage Vcom.

The pixel PX includes a first switching element Q1, a second switchingelement Q2, a third switching element Q3, a first liquid crystalcapacitor Clca and a second liquid crystal capacitor Clcb. The first andsecond liquid crystal capacitors Clca, Clcb may be configured to includea pixel electrode and the common electrode to which the common voltageVcom is applied as two terminals, and to include a liquid crystal layerinterposed therebetween as a dielectric. In some exemplary embodiments,the pixel may further include a sustain capacitor.

The first to third switching elements Q1, Q2, Q3 may be three-terminalelements. A control terminal of the first switching element Q1 isconnected to the gate line GLi, an input terminal thereof is connectedto the data line DLj, and an output terminal thereof may be connected tothe first liquid crystal capacitor Clca. Further, a control terminal ofthe second switching element Q2 is connected to the gate line GLi, aninput terminal thereof is connected to the data line DLj, and an outputterminal thereof may be connected to the second liquid crystal capacitorClcb. Further, a control terminal of the third switching element Q3 isconnected to the gate line GLi, an input terminal thereof is connectedto an output terminal of the second switching element Q2, and an outputterminal thereof may be connected to a reference voltage line (notillustrated).

Terminals included in the first to third switching elements Q1, Q2, Q3and the liquid crystal capacitors Clca, Clcb will be described in moredetail later.

Hereinafter, the operation of the pixel PX in a frame interval will bedescribed.

First, when the gate signal is applied to the gate line GLi, the firstswitching element Q1, the second switching element Q2 and the thirdswitching element Q3 of the pixel PX connected thereto are turned on.

Thus, the data voltage supplied from the data line DLj is applied to afirst sub-pixel electrode as one electrode of the first liquid crystalcapacitor Clca through the first switching element Q1 that is turned on.In this case, the first liquid crystal capacitor Clca may be charged bya difference between the data voltage and the common voltage Vcom. Thefirst liquid crystal capacitor Clca is charged with a relatively largevoltage as compared to a second liquid crystal capacitor Clcb to controlthe liquid crystal. A pixel region defined by the first liquid crystalcapacitor Clca will be referred to as a first sub-pixel PXa or ahigh-pixel.

At the same time, the second and third switching elements Q2, Q3 whichare turned on, electrically connect an input terminal of the secondswitching element Q2 with an output terminal of the third switchingelement Q3. At this time, the data voltage supplied from the data lineDLj is applied to the input terminal of the second switching element Q2,and the reference voltage Vrd having the magnitude smaller than themagnitude (absolute value) of the data voltage is applied the outputterminal of the third switching element Q3, and thus, a predeterminedvoltage having a value between the data voltage and the referencevoltage Vrd is applied to the second sub-pixel electrode which is anelectrode of the second liquid crystal capacitor Clcb, by the voltagedrop. Therefore, the second liquid crystal capacitor Clcb is chargedwith a voltage by a difference between a predetermined voltage smallerthan the data voltage and the common voltage Vcom, and the second liquidcrystal capacitor Clcb is charged with a relatively small voltage ascompared to the first liquid crystal capacitor Clca to control theliquid crystal. A pixel region defined by the second liquid crystalcapacitor Clcb will be referred to as a second sub-pixel pixel PXb or alow-pixel.

In the case of the high-pixel charged with the relatively high voltage,side visibility is vulnerable in a low gradation in which the liquidcrystal is vertically aligned, and in the case of the low-pixel chargedwith the relatively low voltage, the side visibility is vulnerable in anintermediate gradation and a high gradation in which the liquid crystalapproaches a horizontal alignment. That is, the charging voltages of thetwo liquid crystal capacitors Clca, Clcb represent gamma curvesdifferent from each other, and the gamma curve of one pixel voltagerecognized by a viewer becomes a curve obtained by synthesizing them.The synthetic gamma curve from the front is set to coincide with thefront reference gamma curve determined to be most adaptable, and thesynthetic gamma curve from the side surface is set to be in maximallyclose proximity to the front reference gamma curve. By converting theimage data in this way, it is possible to further improve the sidevisibility.

Hereinafter, the components forming the pixel and their arrangement willbe described in further detail.

FIG. 4 is an enlarged plan view of a pixel PX of the exemplary of theliquid crystal display device in FIG. 2. FIG. 5 is a cross-sectionalview taken along the line V-V′ of FIG. 4.

Referring to FIGS. 4 and 5, the liquid crystal display device includes afirst substrate BS1, a second substrate BS2 facing the first substrateBS1 and spaced apart from the first substrate BS1, and a liquid crystallayer 300 interposed between the first substrate BS1 and the secondsubstrate BS2. The first and second substrates BS1, BS2 are transparentor opaque insulating substrates, and may be, for example, a siliconsubstrate, a glass substrate, a plastic substrate or the like.

The gate line GLi extending along approximately the first direction X isdisposed on the first substrate BS1. The gate signal is applied to thegate line GLi to turn on the switching element of a pixel PX connectedthereto.

The first gate electrode 121 and the second gate electrode 122 areformed to protrude from the gate line GLi, and the first gate electrode121 and the second gate electrode 122 may be formed integrally without aphysical boundary. Specifically, the first gate electrode 121 and thesecond gate electrode 122 protrudes downward from the gate line GLi, andthe first gate electrode 121 may be disposed on the right side of thesecond gate electrode 122. Further, the third gate electrode 123 isformed in a region which is superimposed with the extended gate lineGLi. That is, the first to third gate electrodes 121, 122, 123 may bephysically connected to the same gate line GLi, and the same gate signalmay be applied to each of them.

The reference voltage line RLi is formed on the same layer as the gateline GLi and extends substantially parallel to the gate line GLi. Asdescribed above, the reference voltage line RLi provides a referencevoltage, and is connected to the high-pixel and the same data line DLj.However, it is possible to achieve a low-pixel to which a relativelylower voltage is applied as compared to the high-pixel.

The reference voltage line RLi may include a reference voltage electrodeRE, a sustain electrode (not illustrated) and a sustain electrode line(not illustrated). The reference voltage electrode RE protrudes downwardfrom the reference voltage line RLi to have a wide surface, therebybeing able to provide a space which can stably come into contact withthe third drain electrode 153.

Although it is not illustrated in the drawings, the sustain electrodeprotrudes downward from the reference voltage line RLi and may be formedon the surface which is superimposed with the first protruding electrodesection 215. The sustain electrode may form a sustain condenser with afirst drain electrode 151 formed by being superimposed in the upper partand a plurality of protective layers formed therebetween.

In addition, the sustain electrode line (not illustrated) may have ashape which protrudes from the reference voltage line RLi, is partiallysuperimposed with the first sub-pixel electrode 210, and surrounds theoutline of the first sub-pixel electrode 210. In some embodiments, thesustain electrode and/or the sustain electrode line may be omitted andtheir shapes and arrangements may be variously modified.

On the top of the gate line GLi and the reference voltage line RLi, agate insulating film GI is arranged over the whole upper surface of thefirst substrate BS1. The gate insulating film GI is made of aninsulating material, and may electrically insulate a layer located aboveand a layer below the gate insulating film GI. Examples of the materialforming the gate insulating film GI may include silicon nitride (SiNx),silicon oxide (SiOx), silicon oxynitride (SiOxNy) or silicon nitrideoxide (SiNxOy).

The first to third semiconductor layers 131, 132, 133 are disposed onthe gate insulating film GI. Each of the first to third semiconductorlayers 131, 132, 133 is formed in a region overlapped with the first tothird gate electrodes 121, 122, 123, respectively in this order. Thefirst to third semiconductor layers 131, 132, 133 may perform the roleof a channel of a thin film transistor.

A plurality of data lines DLj, DLj+1, the first to third sourceelectrodes 141, 142, 143, and the first to third drain electrode 151,152, 153 are formed on the gate insulating film GI and the first tothird semiconductor layers 131, 132, 133.

The plurality of data lines DLj, DLj+1 extends along approximately thesecond direction Y to intersect with the gate line GLi. The data signalis applied to the data line DLj to charge the pixel electrodes 210, 220connected thereto with the data voltage.

Each of the first to third source electrodes 141, 142, 143 and the firstto third drain electrodes 151, 152, 153 is formed in a region which isat least partially superimposed with the first to third semiconductorlayers 131, 132, 133. An ohmic contact layer (not shown) may be furtherdisposed between a source/drain electrode and the semiconductor layer.

The first source electrode 141 and the second source electrode 142 whichare interconnected without a physical boundary may be formed to protrudefrom the data line DLj in the direction of the first and second gateelectrodes 121, 122. Each of the first and second source electrodes 141,142 may have a shape that is bent in a “U” shape. (The third sourceelectrode 143 will be described later.)

The first drain electrode 151 may be formed on the first gate electrode121 and the first semiconductor layer 131 so as to be spaced apart fromthe first source electrode 141. Similarly, the second drain electrode152 is formed on the second gate electrode 122 and the secondsemiconductor layer 132 so as to be spaced apart from the second sourceelectrode 142. Each of the first and second drain electrodes 151, 152may be electrically connected to the first sub-pixel electrode 210 andthe second sub-pixel electrode 220 through first and second contactholes 161, 162.

Meanwhile, the third source electrode 143 is disposed on the third gateelectrode 123 and the third semiconductor layer 133. The third sourceelectrode 143 is physically connected to the second drain electrode 152.The third drain electrode 153 is formed on the third gate electrode 123and the third semiconductor layer 133 so as to be spaced apart from thethird source electrode 143. Further, the third drain electrode 153 maybe electrically connected to the reference voltage electrode RE throughthe third contact hole 163 and the contact electrode 230.

The gate electrode, the semiconductor layer, the source electrode andthe drain electrode form a thin film transistor which is thethree-terminal switching element illustrated in FIG. 3.

Specifically, the first gate electrode 121 as a control terminal of thefirst switching element Q1 is electrically connected to the gate lineGLi, and the first source electrode 141 as an input terminal iselectrically connected to the data line DLj, and the first drainelectrode 151 as an output terminal is electrically connected to thefirst sub-pixel electrode 210.

The second gate electrode 122 as a control terminal of the secondswitching element Q2 is electrically connected to the gate line GLi, thesecond source electrode 142 as an input terminal is electricallyconnected to the data line DLj, and the second drain electrode 152 as anoutput terminal is electrically connected to the second sub-pixelelectrode 220.

The third gate electrode 123 as a control terminal of the thirdswitching element Q3 is electrically connected to the gate line GLi, thethird source electrode 143 as an input terminal is physically connectedto the second drain electrode 152, and the third drain electrode 153 asan output terminal is electrically connected to a reference voltageelectrode RE.

A protective layer which includes a first protective film PL1, aplanarization layer CF and a second protective film PL2 may be disposedover the entire surface of the plurality of data lines DLj, DLj+1 andthe first to third switching elements Q1, Q2, Q3. The protective layermay be formed of an organic film and/or an inorganic film, and may alsohave a single layer or double layer structure.

The first protective film PL1 may be an inorganic insulating materialsuch as silicon nitride or silicon oxide. The first protective film PL1prevents the wiring and electrodes formed on the lower part from cominginto direct contact with the organic material.

A planarization layer CF made of an organic material may be disposed onthe first protective film PL1. The planarization layer CF is appliedover the entire upper surface of the first substrate BS1 to make uniformthe height of the plurality of components stacked on the first substrateBS1. In some embodiments, a color filter (not shown) is disposed on thefirst protective film, the planarization layer is disposed on the colorfilter, or the planarization layer CF itself may include a color filter.The color filter may be disposed between the plurality of adjacent datalines DLj, DLj+1. The color filter may selectively transmit light of aspecific wavelength band, and different color filters which transmitlight of different wavelength bands for each pixel may be disposed.

The second protective film PL2 may be disposed on the planarizationlayer CF. The second protective film PL2 prevents the lifting-up of theplanarization layer and the color filter, and suppresses thecontamination of the liquid crystal layer due to organic material suchas a solvent introduced from the planarization layer and the colorfilter, thereby being able to prevent a failure such as afterimage thatmay be caused when starting up the screen.

Meanwhile, a contact hole may be defined in the first protective filmPL1, the planarization layer CF and the second protective film PL2 sothat the first to third drain electrode 151, 152, 153 and the referencevoltage electrode RE are at least partially exposed. The first drainelectrode 151 is electrically connected to the first sub-pixel electrode210 through the first contact hole 161, the second drain electrode 152is electrically connected to the second sub-pixel electrode 220 throughthe second contact hole 162, and the third drain electrode 153 iselectrically connected to the reference voltage electrode RE through athird contact hole 163 and a contact electrode 230 formed in the thirdcontact hole 163.

The pixel electrodes 210, 220 and the contact electrode 230 are formedin a region exposed by the second protective film PL2 and the first tothird contact holes 161, 162, 163. The contact electrode 230 has afunction of electrically connecting the reference voltage electrode REexposed through the third contact hole 163 with the third drainelectrode 153. The contact electrode 230 may be formed of the samematerial as the pixel electrodes 210, 220 using an integrated processwhich will be described later.

The pixel electrodes 210, 220 form an electric field with the commonelectrode CE formed on the second substrate BS2, and may control thealignment direction of the liquid crystal molecules LC of the liquidcrystal layer 300 interposed therebetween. The pixel electrodes 210, 220may be a transparent electrode. Examples of the material which forms thetransparent electrodes may include, but not limited to, indium tin oxide(“ITO”), indium zinc oxide (“IZO”) or the like.

The pixel electrodes 210, 220 include a first sub-pixel electrode 210and a second sub-pixel electrode 220 that are spaced apart from eachother. As described above, the first sub-pixel electrode 210 iselectrically connected to the first drain electrode 151 as an outputterminal of the first switching element Q1, and the second sub-pixelpixel electrode 220 may be electrically connected to the second drainelectrode 152 as an output terminal of the second switching element Q2.

The first sub-pixel electrode 210 generally has a substantiallyrectangular shape, and may include a first protruding electrode section215 which protrudes downward. In addition, the first sub-pixelelectrodes 210 may be an electrode having a slit pattern.

Specifically, the slit pattern of the first sub-pixel electrode 210 mayinclude a first stem electrode section 211, a plurality of first branchelectrode sections 212 which is formed by extending from the first stemelectrode section 211, a first slit section 213 which is disposedbetween the plurality of first branch electrode sections 212, and afirst connecting electrode section 214 which is formed in a frameportion of the first sub-pixel electrode 210 to connect the plurality offirst electrode sections 212 with one another.

The first stem electrode section 211 may be formed in a substantiallycross (+) shape, and the first branch electrode section 212 may radiallyextend in a direction tilted from cross-shaped first stem electrodesection 211, e.g. in a direction of approximately 45°. Accordingly, thefirst sub-pixel electrode 210 may have four domains region D1, D2, D3,D4 which are divided by the first stem electrode section 211 and inwhich the first branch electrode section 212 and the first slit section213 are different from each other in directivity. The domain region D1,D2, D3, D4 serves as a director of the liquid crystal molecules LC toform a domain which makes the alignment directions of the liquid crystalmolecules LC different from each other during driving. Thus, as theliquid crystal control improves, the viewing angle increases, thetexture decreases, and additionally, the transmittance and the responsespeed are improved.

At least some of the first electrode sections 212 which extend radiallymay be connected to one another through the first connecting electrodesection 214 that connects the distal ends of the first branch electrodesection 212 with each other. Also, a first protruding electrode section215 is formed below the first sub-pixel electrode 210 and iselectrically connected to the first drain electrode 151 through thefirst contact hole 161 as described above. In this case, the firstsub-pixel electrode 210 may correspond to the high-pixel.

The second sub-pixel electrode 220 may include a second protrudingelectrode section 225, a second stem electrode section 221, a secondbranch electrode section 222, a second slit section 223 and a secondconnecting electrode section 224, and generally has substantially thesame shape and configuration as those of the first sub-pixel electrode210. However, the second sub-pixel pixel electrodes 220 may have arectangular shape in which a vertical length is longer than a horizontallength. An area ratio on the plane between the first sub-pixel electrode210 and the second sub-pixel electrode 220 may be approximately 1:2 ormore and 1:10 or less.

The second sub-pixel electrode 220 is electrically connected to thesecond drain electrode 152 through the second contact hole 162, and maycorrespond to a low-pixel to which a voltage lower than the firstsub-pixel electrode 210 is applied.

The shapes of the first and second sub-pixel electrodes 210, 220 areonly an example, and in some embodiments, the first and second sub-pixelelectrodes may also be disposed in the form of being bent to the gateline and the data line, and may also be deformed to conform to thevarious shapes of the branch electrode section and the slit section.

In some embodiments, a shield electrode (not shown) may be disposed in aregion which is superimposed with the plurality of data lines DLj,DLj+1. The shield electrode (not shown) is formed on top of the dataline DLj, DLj+1 to serve to prevent the inter-electrode interferenceproblem which may be caused by a sudden change in polarity of the datavoltage, or a problem in which the liquid crystal molecules located onthe top of the data line DLj, DLj+1 are directly affected by the datavoltage. For example, the same voltage as the reference voltage may beapplied to the shield electrode (not illustrated) or the shieldelectrode may be in a floating state. The shield electrode and thereference voltage line may also be in a state of being electricallyconnected to each other.

Meanwhile, an alignment film 400 may be disposed on the sub-pixelelectrodes 210, 220, the contact electrode 230, and the secondprotective film PL2. Also, a photo-curable layer 550 (see FIG. 6) may beformed on the alignment film 400.

Next, the second substrate BS2 will be described. The second substrateBS2 may be an upper substrate as positioned relative to the firstsubstrate BS1. A light shielding member BM, an overcoat layer OC and acommon electrode CE may be disposed on the second substrate BS2.

The light shielding member BM may be disposed at the boundary betweenthe plurality of color filters. More specifically, the light shieldingmember may be disposed in a region which is superimposed with aplurality of data lines DLj, DLj+1, the gate line GLi and the first tothird switching elements Q1, Q2, Q3 formed on the first substrate BS1.For example, the light-shielding member BM may also be a black matrix.Alternatively, the light shielding member may also be formed on the topof the color filter of the first substrate, unlike the configurationillustrated in the figures.

The overcoat layer OC may act as a planarization layer and may be formedon the second substrate 200 and the light shielding member BM. Thecommon electrode CE may be disposed on the overcoat layer OC. The commonvoltage is applied to the common electrode CE, and thus, the commonelectrode may generate an electric field together with the pixelelectrodes 210, 220 formed on the first substrate BS1 to control thealignment direction of the liquid crystal molecules LC of the liquidcrystal layer 300 interposed therebetween. The common electrode CE maybe a transparent electrode, and the common electrode CE may be apattern-less electrode having no slit pattern, however the commonelectrode may also have a predetermined pattern without being limitedthereto.

A vertical alignment inducing layer 650 may be formed on the commonelectrode CE. Hereinafter, the alignment film 400, the photo-curablelayer 550 and the vertical alignment inducing layer 650 will bedescribed in detail with reference to FIG. 6.

FIG. 6 is a cross-sectional view taken along the line VI-VI′ of theexemplary liquid crystal display in FIG. 4. FIG. 6 schematicallyillustrates the alignment of the liquid crystal molecules in an initialstate in which no electric field is applied to the liquid crystaldisplay device.

Referring to FIGS. 4 and 6, the liquid crystal layer 300 includes firstliquid crystal molecules 310 adjacent to the surface of the alignmentfilm 400 disposed on the lower substrate including the first substrateBS1, and second liquid crystal molecules 320 adjacent to the surface ofthe common electrode CE disposed on the upper substrate including thesecond substrate BS2.

The alignment film 400 is disposed on the second protective film PL2formed on the first substrate BS1 and the pixel electrodes 210, 220. Inan exemplary embodiment, the alignment film 400 may be a verticalalignment type liquid crystal alignment film formed of a polyimide inwhich an imide group (—CONHCO—) is contained within a repeating unit ofa main chain and one or more side chains are connected to the mainchain. A portion of the side chains includes at least one verticalalignment group selected from one or more of an alkyl group, hydrocarbonderivatives terminally substituted by an alkyl group, hydrocarbonderivatives terminally substituted by a cycloalkyl group, andhydrocarbon derivatives terminally substituted by aromatic hydrocarbon.

At least a portion of the side chains of the alignment film 400 mayfurther contain a side chain substituted by a polymerization initiatorin addition to the vertical alignment group. The polymerizationinitiator may be a photopolymerization initiator. In this case, thephotopolymerization initiator absorbs ultraviolet (“UV”) light and isdecomposed into radicals, which promote the polymerization reaction.

In exemplary embodiments, the polymerization initiator may include oneor more of acetophenone, benzoin, benzophenone, diethoxyacetophenone,phenylketone, thioxanthone, 2-hydroxy-2-methyl-1-phenylpropane-1-on,benzyl dimethyl tar, 4-(2-hydroxyethoxy) phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, methyl o-benzoyl benzoicacid, 4-phenyl benzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide,(4-benzoyl-benzyl) trimethylammonium chloride, bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide, diphenyl(2,4,6-trimethyl benzoyl)-phosphine oxide,2-hydroxy-2-methylpropionitrile, 2,2′-{azobis (2-methyl-N-[1,1′-bis(hydroxymethyl)-2-hydroxyethyl) propionamide], acrylic acid[(2-methoxy-2-phenyl-2-benzoyl)-ethyl] ester, phenyl2-acryloyloxy-2-propyl ketone, phenyl 2-methacryloyloxy-2-propyl ketone,4-isopropyl phenyl, 2-acryloyloxy-2-propyl ketone, 4-chlorophenyl2-acryloyloxy-2-propyl ketone, 4-dodecyl phenyl 2-acryloyloxy-2-propylketone, 4-methoxyphenyl, 2-acryloyloxy-2-propyl ketone, 4-acryloyloxyphenyl 2-hydroxy-2-propyl ketone, 4-methacryloyloxyphenyl2-hydroxy-2-propyl ketone, 4-(2-acryloyloxyethoxy)-phenyl2-hydroxy-2-propyl ketone, 4-(2-acryloyloxyethoxy)-phenyl2-hydroxy-2-propyl ketone, 4-(2-acryloyloxyethoxy)-benzo,4-(2-acryloyloxy ethylthio)-phenyl 2-hydroxy-2-propyl ketone, 4-N,N′-bis-(2-acryloyloxyethyl)-aminophenyl 2-hydroxy-2-propyl ketone,4-acryloyloxyphenyl 2-acryloyloxy-2-propyl ketone,4-methacryloyloxyphenyl 2-methacryloyloxy-2-propyl ketone,4-(2-acryloyloxyethoxy)-phenyl 2-acryloyloxy-2-propyl ketone,4-(2-acryloyloxyethoxy)-phenyl 2-acryloyloxy-2-propyl ketone,dibenzylketone, benzoin alkyl ether, benzoin methyl ether, benzoin ethylether, benzoin isopropyl ether, benzoin isobutyl ether, dialkylacetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethylketal, acylphosphine, and α-aminoketone. However, the above-mentionedpolymerization initiators are not limited thereto.

In addition to the vertical alignment group and the polymerizationinitiator, at least a portion of the side chain of the alignment film400 may further contain a side chain substituted by an ion scavenger.The ion scavenger may be a cationic scavenger or an anionic scavenger.The ion scavenger may capture ionic impurities in the liquid crystallayer 300 to improve the voltage maintenance of the liquid crystaldisplay device.

A photo-curable layer 550 may be formed on the top of the alignment film400. The photo-curable layer 550 may be understood as a layer formed onsubstantially the entire upper surface of the alignment film 400,despite the illustrated configuration. The photo-curable layer 550 maybe formed of a polymer compound in which single molecules including thevertical alignment group and the photo-curable agent are chemicallybonded to each other. The photo-curable layer 550 is cured while beingaligned along the tilted direction of the liquid crystal molecules. Inparticular, the first liquid crystal molecules 310 connected to thephoto-curable layer 550 may maintain the pre-tilt even in a state inwhich no electric field is formed. As a result, when an electric fieldfor driving is formed in the liquid crystal display device, the liquidcrystal molecules LC are tilted in the pre-tilt direction, and thus, theresponse speed of the liquid crystal display device can be improved.

The photo-curable agent may be a reactive mesogen (“RM”). The termmesogen refers to a photo cross-linkable low molecular or high-molecularcopolymer including a mesogen group having a liquid crystal nature, andwhich initiates a chemical reaction such as polymerization reaction whenabsorbing light of a particular wavelength. The reactive mesogen may be,for example, an acrylate, methacrylate, epoxy, oxetane, vinyl-ether,styrene, thioether, thiol, or thiolen group. In addition, the reactivemesogen may be a material of a rod-shaped, banana-shaped, board-shapedor disk-shaped structure.

Meanwhile, the vertical alignment inducing layer 650 may be formed belowthe common electrode CE. The vertical alignment inducing layer 650 mayalso be understood by a layer formed on substantially the entire lowersurface of the common electrode CE despite the illustratedconfiguration. The vertical alignment inducing layer is formed from avertical alignment inducer compound. At one end, the molecules of thevertical alignment inducer include an affinity liquid crystal grouphaving a high affinity with the liquid crystal molecules LC, and at theother end, the molecules of the vertical alignment inducer include ahydrophilic group that has high affinity with the common electrode CE,as compared to the liquid crystal molecules LC.

In an exemplary embodiment, the affinity liquid crystal group mayinclude an alkyl group, a cycloalkyl group, an aryl group, an estergroup and an azo group. In an exemplary embodiment, the hydrophilicgroup may include, but is not limited to, a group capable of hydrogenbonding or which has a high dielectric constant or polarity, such as,for example, a hydroxyl group, an amine group, an amino group, acarboxyl group, a silane group, a siloxane group and a thiol group.

In an exemplary embodiment, the vertical alignment inducer may be achain-type (i.e. linear) molecule having the structure of Formula 1below.

The hydrophilic group of the vertical alignment inducer may be alignedon the surface of the common electrode CE through a hydrogen bond with,for example, a hydroxyl group (—OH) exposed to the surface of the commonelectrode CE. Meanwhile, since the affinity liquid crystal group has ahigher affinity with the liquid crystal molecules LC as compared to thecommon electrode CE, it can be aligned in the direction of the liquidcrystal layer 300. The vertical alignment inducer may be verticallyself-aligned on the surface of the common electrode CE through a manpower and/or a repulsive force is formed by the vertical alignmentinducer with the common electrode CE and the liquid crystal moleculesLC. Thus, a vertical alignment inducing layer 650 in which the liquidcrystal molecules LC may be aligned may be formed on the upper substrateincluding the second substrate BS2, without forming a separate alignmentfilm. The vertical alignment inducer may be included, but not limitedto, in a proportion from about 10 ppm up to about 30 weight percent (wt%), as compared to the total weight of the liquid crystal composition.

Meanwhile, the alignment of the first liquid crystal molecules 310formed in the first domain region of D1 is different from the firstliquid crystal molecules 310 formed in the second domain region D2 inthe liquid crystal alignment direction. For example, the first liquidcrystal molecules 310 formed in the first domain region D1 may bealigned to have approximately a first pre-tilt angle θ1, and the firstliquid crystal molecules 310 formed in the second domain region D2 maybe aligned to have a pre-tilt angle which has the same magnitude as thefirst pre-tilt angle θ1 but has a direction opposite thereto. In thisway, as described above, it is possible to improve the viewing angle andimprove the response speed, by forming the domains in which thealignment directions of the liquid crystal molecules are different fromeach other.

Meanwhile, the second liquid crystal molecules 320 are aligned to have asecond pre-tilt angle θ2 and may be vertically aligned as compared tothe first liquid crystal molecules 310. In an exemplary embodiment, thesecond pre-tilt angle θ2 may be from 0° to about 2° or less, and thefirst pre-tilt angle θ1 may be aligned at an angle of greater than 1° ormore than the second pre-tilt angle θ2. As used herein, the first andsecond pre-tilt angles θ1, θ2 refer to the magnitude of the angle inwhich the long axes of the first and second liquid crystal molecules310, 320 are tilted with respect to imaginary normal line of the firstand second substrates BS1, BS2. For example, when the liquid crystalmolecules are aligned vertically with respect to the surface, thepre-tilt angle of the liquid crystal molecules is 0°.

In an initial state in which no electric field is applied to the liquidcrystal display device, the first liquid crystal molecules 310 adjacentto the surface of the lower substrate have the large pre-tilt angle, andthe second liquid crystal molecules 320 adjacent to the surface of theupper substrate are substantially vertically aligned. Thus, there is aneffect of being able to improve the soil or dark part caused bycollision of the alignment directions of the first liquid crystalmolecules 310 and the second liquid crystal molecules 320.

In addition, since an alignment film is disposed on top of the lowersubstrate and the alignment angle of the liquid crystal molecules may beadjusted without forming a separate alignment film on the uppersubstrate, the process becomes simplified. Further, since there is noneed to use, maintain and manage different compositions and/or types ofalignment films, there is a reduction in the cost.

Hereinafter, exemplary embodiments of a method of manufacturing theliquid crystal display device according to the present invention will bedescribed.

FIG. 7 is a flowchart illustrating an exemplary embodiment of a processfor manufacturing the liquid crystal display device according to thepresent invention. FIGS. 8 to 14 are cross-sectional views illustratingthe individual steps of the manufacturing process of FIG. 7 in astepwise manner.

Referring to FIGS. 7 and 8, a lower substrate including the firstsubstrate BS1, and an upper substrate including the second substrate BS2are prepared (S110, S130). As described previously, the lower substrateincludes a gate line (not illustrated), a reference voltage line (notillustrated), a gate insulating film GI, a data line (not illustrated),a gate/source/drain electrode, protective film layers PL1, PL2, a colorfilter CF and pixel electrodes 211, 212 on the first substrate BS1. Theupper substrate includes a light shielding member BM, an overcoat layerOC and a common electrode CE on the second substrate BS2. The alignmentfilm 401 may be disposed on the upper surface of the lower substrate(S120).

The components such as the gate line, the reference voltage line, thedata line, the semiconductor layer and the gate/source/drain electrodesincluded in the lower substrate and the upper substrate may be formed byforming a metal layer on the substrate and by patterning the metallayer. The patterning may use a mask process, and other methods capableof forming the pattern may be used in addition to this method.

The pixel electrodes 211, 212 may be disposed on the top of the lowersubstrate. The pixel electrodes 211, 212 may be a transparent electrodethat is made of indium tin oxide (ITO) and indium zinc oxide (IZO). Thepixel electrodes 211, 212 have slit patterns and include the stemelectrode section and the branch electrode section as described above.Further, between the branch electrode sections of the pixel electrode212, a part of the lower substrate may be exposed through the slitsection.

The alignment film 401 may be formed by coating or printing thealignment film composition on the upper surface of the lower substrate.As described previously, the alignment film 401 is a polyimide whichcontains the imide group within the repeating unit of the main chain.The polyimide has a vertical alignment group (not illustrated), apolymerization initiator 411 and/or an ion scavenger (not illustrated)in a side chain. Since the alignment film 401 may have substantially thesame configuration as the alignment film 400 of FIG. 6, a detaileddescription thereof will not be provided.

The common electrode CE may be disposed on the top of the uppersubstrate. The common electrode CE may be a transparent electrode likethe pixel electrodes 211, 212. In addition, the common electrode CE maybe a pattern-less electrode having no slit pattern, but may have apredetermined pattern, without being limited thereto.

Next, referring to FIGS. 7 and 9, a liquid crystal layer 301, whichincludes photo-curable agent 501, a vertical alignment inducer 601 andliquid crystal molecules LC having negative dielectric anisotropy, isinterposed between the lower substrate and the upper substrate (S140).The liquid crystal layer 301 may be formed through a liquid crystaldropping process and both substrates can be bonded to each other, oralternatively, a liquid crystal injection process may be used afterbonding both the substrates.

The liquid crystal molecules LC in the liquid crystal layer 301 includefirst liquid crystal molecules 311 adjacent to the surface of thealignment film 401, and second liquid crystal molecules 321 adjacent tothe surface of the common electrode CE. In the initial state in which noelectric field is formed, the first liquid crystal molecules 311 may besubstantially vertically aligned by the vertical alignment group of thealignment film 401. Here, the expression “substantially verticallyaligned” means that the first liquid crystal molecules 311 are alignedin the range from about 88° to about 90° or less with respect to thefirst substrate BS1.

After bonding, in order to improve the spreading characteristics anduniformity of the liquid crystal molecules LC, an annealing process maybe performed.

Referring to FIGS. 10(A) and 10(B), in which FIG. 10(B) is an enlargedview of the circled portion of FIG. 10(A), after forming the liquidcrystal layer 301 including the vertical alignment inducer 601, thevertical alignment inducing layer 651 may be formed on the surface ofthe common electrode CE. As described above, one end of the verticalalignment inducer 601 having a hydrophilic group may be aligned in thedirection of the common electrode CE through a hydrogen bond between ahydroxyl group exposed to the surface of the common electrode CE.Meanwhile, since a functional group capable of performing the hydrogenbonding is not present on the surface of the alignment film 401, thevertical alignment inducer 601 has high chemical selectivity to thecommon electrode CE, as compared to the alignment film 401. Therefore,it is possible to selectively induce the formation of vertical alignmentinducing layer 651 only on the surface of the common electrode CE.

In particular, when performing the liquid crystal dropping process,after dropping the liquid crystal composition including the verticalalignment inducer 601 on the upper substrate on which the commonelectrode CE is formed, the lower substrate and the upper substrate arebonded to each other. At this time, after a sufficient amount of time topredominantly form the vertical alignment inducing layer 651 on thesurface of the common electrode CE of the upper substrate onto which theliquid crystal composition is dropped, both substrates are bonded tophysically further increase the selectivity of the vertical alignmentinducing layer 651.

Meanwhile, the other end of the vertical alignment inducer 601 having anaffinity liquid crystal group is aligned in the direction of the liquidcrystal layer 301. The vertical alignment inducer 601 therefore may beself-aligned vertically with respect to the surface of the commonelectrode CE. Thus, the second liquid crystal molecules 321 adjacent tothe affinity liquid crystal group of the vertical alignment inducer 601may be aligned substantially vertically with respect to the surface ofthe common electrode CE.

Next, referring to FIGS. 7 and 11, by forming an electric field betweenthe lower substrate and the upper substrate of the liquid crystaldisplay device, the liquid crystal molecules LC may be obliquely alignedin a direction perpendicular to the electric field formed between thecommon electrode CE and the pixel electrodes 211, 212 (S150).

Next, referring to FIGS. 7 and 12, by irradiating the ultraviolet (UV)light at the same time in which the electric field is formed (i.e.electric field is present) and by initiating photopolymerizationreaction of the photo-curable agent 501 by the polymerization initiator411 included in the alignment film 401, the photo-curable layer 551 canbe formed (S160). The photo-curable agent 501 may be, for example, areactive mesogen. The photo-curable layer 551 may be a polymer compoundin which single molecules containing the vertical alignment group andthe photo-curable agent 501 are chemically bonded to each other.

Specifically, the liquid crystal molecules LC having a negativedielectric anisotropy are obliquely aligned by an electric field, andthe vertical alignment group of the alignment film 401 and thepolymerization initiator 411 are arranged in the same direction as thefirst liquid crystal molecules 311, by the arrangement of the liquidcrystal molecules LC, in particular, the first liquid crystal molecules311. At this time, while double bonding of the photoreactive groups ofthe photo-curable agent 501 is initiated by the polymerization initiator411, the photoreactive groups form crosslinks with the surroundingphotoreactor portion.

At this time, the content of the photo-curable agent 501 in the liquidcrystal layer 301 gradually decreases, since the reduced photo-curableagent 501 is being used to form the photo-curable layer 551.

Meanwhile, since the vertical alignment inducing layer 651 does notcontain the polymerization initiator 411, the polymerization reactiondoes not proceed in the vertical alignment inducing layer 651.

FIG. 13 is a diagram illustrating that the alignment direction of thefirst liquid crystal molecules 311 are fixed or stabilized by thepre-tilt photo-curable layer 551. That is, the first liquid crystalmolecules 311 have a first pre-tilt angle θ1 even when no electric fieldis present. Meanwhile, the tilted alignment of the second liquid crystalmolecules 321 is not maintained when the electric field is absent and issubstantially vertically aligned to have a second pre-tilt angle θ2smaller than the first pre-tilt angle θ1. The reason is that, asdescribed above in FIG. 10, the vertical alignment inducer 601 isself-aligned vertically with respect to the surface of the commonelectrode CE and the vertical alignment inducing layer 651 formed by thevertical alignment inducer is not cured by the photo-curable agent 501,and the vertical alignment inducing layer 651 induces the verticalalignment of the second liquid crystal molecules 321. Thus, it ispossible to differently control the pre-tilt angles of the first liquidcrystal molecules 311 and the second liquid crystal molecules 321. And,since it is not necessary to form an alignment film on the uppersubstrate, there is an advantage of being able to reduce themanufacturing cost and simplify the process.

Referring to FIGS. 7 and 14, ultraviolet light is irradiated again butis done so in a state in which no electric field is formed (i.e.electric field is absent) in order to remove any remaining photo-curableagent 501 (S170). By removing the residual photo-curable agent 501remaining in the liquid crystal layer 301, it is possible to preventafterimage or dirt failure that may occur in the liquid crystal displaydevice. Thereafter, although it is not illustrated, it is possible tomanufacture a curved liquid crystal display device through a processwhich encompasses bending both ends of the liquid crystal displaydevice.

Hereinafter, another exemplary embodiment of a process of manufacturingprocess a liquid crystal display device according to the presentinvention will be described.

FIG. 15 is a flowchart illustrating an exemplary embodiment of themanufacturing process steps for the liquid crystal display deviceaccording to the present invention. FIGS. 16 to 22 are cross-sectionalviews illustrating the separate manufacturing process steps of FIG. 15in a stepwise manner. However, in order not to obscure the essence ofthe invention, additional methods of manufacturing the liquid crystaldisplay using substantially the same or similar configurations as themethod of manufacturing the liquid crystal display device will not bedescribed, but will instead be clearly understood by those skilled inthe art in view of the accompanying drawings.

Referring to FIGS. 15 and 16, a lower substrate including the firstsubstrate BS1, and an upper substrate including the second substrate BS2are prepared. (S210, S230) An alignment film 402 may be disposed on theupper surface of the lower substrate (S220).

The alignment film 402 may be formed by coating or printing an alignmentfilm composition on the upper surface of the lower substrate. Asdescribed previously, the alignment film 402 includes a polyimide havinga main chain including an imide group within the repeating unit of themain chain, and one or more side chain connected to the main chain. Theside chain may include a vertical alignment group (not shown), thepolymerization initiator 412 and/or an ion scavenger (not shown).

In addition, this embodiment is different from the previously describedmanufacturing method of the present invention in that the alignment film402 further contains a photo-curable agent 502. The photo-curable agent502 may also be connected to the side chain of polyimide forming thealignment film 402, and may also be included in the alignment film 402composition.

Next, referring to FIGS. 15 and 17, a liquid crystal layer 302 includinga vertical alignment inducer 602 and liquid crystal molecules 312, 322having negative dielectric anisotropy are interposed between the uppersubstrate and the lower substrate (S240). In this case, the liquidcrystal layer 302 is formed through the liquid crystal dropping processand both substrates may be bonded, or alternatively, the liquid crystalinjection process may be used after bonding both substrates.

The liquid crystal molecules in the liquid crystal layer 302 includefirst liquid crystal molecules 312 adjacent to the surface of thealignment film 402, and second liquid crystal molecules 322 adjacent tothe surface of the common electrode CE. In the initial state in which noelectric field is formed, the first liquid crystal molecules 312 may besubstantially vertically aligned by the vertical alignment group of thealignment film 402.

After bonding, an annealing process may be performed to improve thespreading characteristics and uniformity of the liquid crystal moleculesLC.

Meanwhile, after forming the liquid crystal layer 302, a heat treatmentprocess of applying heat from the bottom of the lower substrate isperformed. The photo-curable agent 502 contained in the alignment film402 may be eluted to the liquid crystal layer 302 as a result of theheat treatment process. The heat treatment process may also be performedafter forming the vertical alignment inducing layer 652. Although it isnot illustrated in the drawings, some of the photo-curable agent remainson the surface of the alignment film without being eluted to the liquidcrystal layer and photo-curing may occur.

Referring to FIGS. 18(A) and 18(B), in which FIG. 18(B) is an enlargedview of the circled portion of FIG. 18(A), after forming the liquidcrystal layer 302 which contains the vertical alignment inducer 602, thevertical alignment inducing layer 652 may be formed on the surface ofthe common electrode CE. The vertical alignment inducer 602 does notform the vertical alignment inducing layer on the surface of thealignment film 402, and may selectively form the vertical alignmentinducing layer 652 only on the surface of the common electrode CE

Next, referring to FIGS. 15 and 19, by forming an electric field betweenthe lower substrate and the upper substrate of the liquid crystaldisplay device, the liquid crystal molecules LC may be obliquely alignedin a direction perpendicular to the electric field formed between thecommon electrode CE and the pixel electrodes 211, 212 (S250).

Next, referring to FIGS. 15 and 20, by irradiating with ultraviolet (UV)light at the same time in which the electric field is formed, thephotopolymerization reaction of the photo-curable agent 502 by thepolymerization initiator 412 contained in the alignment film 402 isinitiated, and the photo-curable layer 552 is formed (S260). Thephoto-curable agent 502 may be, for example, a reactive mesogen. Thephoto-curable layer 552 may be a polymer compound formed when singlemolecules containing the vertical alignment group and the photo-curableagent 502 are chemically bonded to each other. That is, thephoto-curable layer 552 is cured in the tilted direction of the verticalalignment group of the first liquid crystal molecules 312 and thealignment film 402.

FIG. 21 is a diagram illustrating that the alignment direction of thefirst liquid crystal molecules 312 is fixed or stabilized by thepre-tilt photo-curable layer 552. That is, even when no electric fieldis formed or present, the first liquid crystal molecules 312 have afirst pre-tilt angle θ1, and meanwhile, the tilted alignment of thesecond liquid crystal molecules 322 is not maintained when the electricfield is canceled and the second liquid crystal molecules aresubstantially vertically aligned to have a second pre-tilt angle θ2smaller than the first line pre-tilt angle θ1.

Referring to FIGS. 15 and 22, ultraviolet light is irradiated again in astate in which no electric field is formed (i.e. absent) to remove theremaining photo-curable agent 502 (S270). Thereafter, although notillustrated, it is possible to manufacture a curved liquid crystaldisplay device through the process of bending both ends of the liquidcrystal display device. The method of manufacturing a liquid crystaldisplay device according to this embodiment has an effect of being ableto reduce the manufacturing cost, by utilizing a liquid crystalcomposition which does not contain the photo-curable agent.

While the present invention has been particularly illustrated anddescribed with reference to exemplary embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and detail may be made therein without departing from the spiritand scope of the present invention as defined by the following claims.The exemplary embodiments should be considered in a descriptive senseonly and not for purposes of limitation.

What is claimed is:
 1. A method of manufacturing a liquid crystaldisplay device, the method comprising: preparing a first substratehaving a pixel electrode formed on an upper surface of the firstsubstrate; forming an alignment film on the pixel electrode; preparing asecond substrate having a common electrode formed on an upper surface ofthe second substrate and disposing the second substrate such that thecommon electrode faces the alignment film; interposing a liquid crystallayer comprising a vertical alignment inducer between the alignment filmand the common electrode; forming a vertical alignment inducing layerfrom the vertical alignment inducer; forming an electric field betweenthe pixel electrode and the common electrode; and irradiating light inthe presence of the electric field to form a photo-curable layer on asurface of the alignment film.
 2. The method of claim 1, wherein theliquid crystal layer comprises a photo-curable agent.
 3. The method ofclaim 2, wherein the photo-curable layer is formed by polymerization ofthe photo-curing agent present in the liquid crystal layer.
 4. Themethod of claim 1, wherein the alignment film comprises a photo-curableagent.
 5. The method of claim 4, wherein the photo-curable layer isformed by polymerization of the photo-curing agent present in thealignment film.
 6. The method of claim 1, wherein the vertical alignmentinducer is a linear molecule having a hydrophilic group capable ofhydrogen bonding at one end, and an affinity crystal group having a highaffinity with the liquid crystal molecules at the other end, wherein theend having the hydrophilic group is aligned in the direction of thecommon electrode, and the end having the affinity crystal group isaligned in the direction of the liquid crystal layer to form a verticalalignment inducing layer on the surface of the common electrode.
 7. Themethod of claim 1, further comprising: irradiating light in the absenceof the electric field after the forming of the photo-curable layer. 8.The method of claim 7, wherein the liquid crystal molecules adjacent tothe photo-curable layer have a first pre-tilt angle, and the liquidcrystal molecules adjacent to the vertical alignment inducing layer havea second pre-tilt angle smaller than the first pre-tilt angle.